Thor and Rai are twins who live on an advanced space colony called Juno. Things take a nasty turn one day when they are kidnapped by the Federal Army's Special Forces and abandoned on the hostile prison planet Kimaera. A cycle on Kimaera consists of 181 days of scorching heat and 181 nights of below-freezing temperatures - not to mention it is populated almost entirely by carnivorous plants. The convicts on Kimaera have found only one means of survival - reverting back to the law of beasts. For the strong-willed Thor adjustment comes naturally; but for his naive and weaker brother Rai, things do not go as well. Thor must now use all his wits, strength and courage to endure life as a member of Kimaeran society, rise above the rest, and take the only ticket off this planet: becoming the Beast King.
Only one chapter of Verdant Lord was available at the time of this recommendation, but I definitely had a very similar feeling as Jyu Oh Sei. Both involve worlds where plants have taken over and freakish monsters are keeping humans at bay.